First, we put water in a jar and dropped a couple of raisins in it. They of course sunk!

Then, we put vinegar in a jar and added some raisins.

we then put baking soda in it and watched.

The raisins started to rise off the bottom of the jar when there were enough air bubbles surrounding them. They float to the top, the bubbles release the carbon dioxide, and then they sink to the bottom of the jar again.